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Indirect approach to invariant point determination for SLR and VLBI systems: an assessment / John Dawson in Journal of geodesy, vol 81 n° 6-8 (June - August 2007)  

Public [article]  inJournal of geodesy > vol 81 n° 6-8 (June - August 2007) . - pp 433 - 441 Titre : Indirect approach to invariant point determination for SLR and VLBI systems: an assessment Type de document : Article/Communication Auteurs : John Dawson, Auteur ; Pierguido Sarti, Auteur ; G.M. Johnston, Auteur ; et al., Auteur Année de publication : 2007 Article en page(s) : pp 433 - 441 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] erreur systématique [Termes IGN] interférométrie à très grande base [Termes IGN] invariant [Termes IGN] point de liaison (géodésie) [Termes IGN] télémétrie laser sur satellite Résumé : (Auteur) We assess the accuracy of some indirect approaches to invariant point (IVP), or system reference point, determination of satellite laser ranging (SLR) and very long baseline interferometry (VLBI) systems using both observed and simulated survey data sets. Indirect IVP determination involves the observation of targets located on these systems during specific rotational sequences and by application of geometrical models that describe the target motion during these sequences. Of concern is that most SLR and VLBI systems have limited rotational freedom thereby placing constraint on the reliability of parameter estimation, including the IVP position. We assess two current approaches to IVP analysis using survey data observed at the Yarragadee (Australia) SLR and the Medicina (Italy) VLBI sites and also simulated data of a large rotationally constrained (azimuth-elevation) VLBI system. To improve reliability we introduce and assess some new geometric conditions, including inter-axis, inter-circle and inter-target conditions, to existing IVP analysis strategies. The error component of a local tie specifically associated with the indirect determination of SLR and VLBI IVP is less than 0.5 mm. For systems with significant rotational limits we find that the inter-axis and inter-circle conditions are critical to the computation of unbiased IVP coordinates at the sub-millimetre level. When the inter-axis and inter-circle geometric conditions are not imposed, we retrieve biased vertical coordinates of the IVP (in our simulated VLBI system) in the range of 1.2–3.4 mm. Using the new geometric conditions we also find that the axis-offset estimates can be recovered at the sub- millimetre accuracy (0.5 mm). Copyright Springer Numéro de notice : A2007-241 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0125-x En ligne : https://doi.org/10.1007/s00190-006-0125-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28604 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-07062	RAB	Revue	Centre de documentation	En réserve L003	Disponible
266-07061	RAB	Revue	Centre de documentation	En réserve L003	Disponible

The impact of radio source structure on European geodetic VLBI measurements / V. Tornatore in Journal of geodesy, vol 81 n° 6-8 (June - August 2007)  

Public [article]  inJournal of geodesy > vol 81 n° 6-8 (June - August 2007) . - pp 469 - 478 Titre : The impact of radio source structure on European geodetic VLBI measurements Type de document : Article/Communication Auteurs : V. Tornatore, Auteur ; Patrick Charlot, Auteur Année de publication : 2007 Article en page(s) : pp 469 - 478 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] données ITGB [Termes IGN] European VLBI network [Termes IGN] interférométrie à très grande base [Termes IGN] rayonnement cosmique Résumé : (Auteur) European geodetic very long baseline interferometry (VLBI) sessions (also known as EUROPE sessions) have been carried out on a regular basis for the past 15 years to study relative crustal motions within Europe. These sessions are based on observations of extragalactic radio sources, which serve as distant fiducial marks to establish an accurate and stable celestial reference frame for long-term geodetic measurements. The radio sources, however, are not always point-like on milliarcsecond scales, as VLBI imaging has revealed. In this work, we quantify the magnitude of the expected effect of intrinsic source structure on geodetic bandwidth synthesis delay VLBI measurements for a subset of 14 sources regularly observed during the EUROPE sessions. These sources have been imaged at both X-band (8.4 GHz) and S-band (2.3 GHz) based on dedicated observations acquired with the European VLBI Network (EVN) in November 1996. The results of this calculation indicate that the reference source 0457+024 causes significant structural effects in measurements obtained on European VLBI baselines (about 10 picoseconds on average), whereas most of the other sources produce effects that are only occasionally larger than a few picoseconds. Applying the derived source structure models to the data of the EUROPE5-96 session carried out at the same epoch as the EVN experiment shows no noticeable changes in the estimated VLBI station locations. Copyright Springer Numéro de notice : A2007-242 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-007-0146-0 En ligne : https://doi.org/10.1007/s00190-007-0146-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28605 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-07062	RAB	Revue	Centre de documentation	En réserve L003	Disponible
266-07061	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Combined Earth orientation parameters based on homogeneous and continuous VLBI and GPS data / Daniela Thaller in Journal of geodesy, vol 81 n° 6-8 (June - August 2007)  

Public [article]  inJournal of geodesy > vol 81 n° 6-8 (June - August 2007) . - pp 529 - 541 Titre : Combined Earth orientation parameters based on homogeneous and continuous VLBI and GPS data Type de document : Article/Communication Auteurs : Daniela Thaller, Auteur ; Manuela Krügel, Auteur ; Markus Rothacher, Auteur ; et al., Auteur Année de publication : 2007 Article en page(s) : pp 529 - 541 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] Bernese [Termes IGN] données GPS [Termes IGN] données ITGB [Termes IGN] mouvement du pôle [Termes IGN] nutation [Termes IGN] point de liaison (géodésie) [Termes IGN] rotation de la Terre Résumé : (Auteur) The CONT02 campaign is of great interest for studies combining very long baseline interferometry (VLBI) with other space-geodetic techniques, because of the continuously available VLBI observations over 2 weeks in October 2002 from a homogeneous network. Especially, the combination with the Global Positioning System (GPS) offers a broad spectrum of common parameters. We combined station coordinates, Earth orientation parameters (EOPs) and troposphere parameters consistently in one solution using technique- specific datum-free normal equation systems. In this paper, we focus on the analyses concerning the EOPs, whereas the comparison and combination of the troposphere parameters and station coordinates are covered in a companion paper in Journal of Geodesy. In order to demonstrate the potential of the VLBI and GPS space-geodetic techniques, we chose a sub-daily resolution for polar motion (PM) and universal time (UT). A consequence of this solution set-up is the presence of a one-to-one correlation between the nutation angles and a retrograde diurnal signal in PM. The Bernese GPS Software used for the combination provides a constraining approach to handle this singularity. Simulation studies involving both nutation offsets and rates helped to get a deeper understanding of this singularity. With a rigorous combination of UT1–UTC and length of day (LOD) from VLBI and GPS, we showed that such a combination works very well and does not suffer from the systematic effects present in the GPS-derived LOD values. By means of wavelet analyses and the formal errors of the estimates, we explain this important result. The same holds for the combination of nutation offsets and rates. The local geodetic ties between GPS and VLBI antennas play an essential role within the inter-technique combination. Several studies already revealed non-negligible discrepancies between the terrestrial measurements and the space-geodetic solutions. We demonstrate to what extent these discrepancies propagate into the combined EOP solution. Copyright Springer Numéro de notice : A2007-243 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0115-z En ligne : https://doi.org/10.1007/s00190-006-0115-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28606 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-07062	RAB	Revue	Centre de documentation	En réserve L003	Disponible
266-07061	RAB	Revue	Centre de documentation	En réserve L003	Disponible